you can still get PCI-X hardware raid controllers , the 3-Ware/LSI 7000 or 9000 series I think are quite cheap. even with the full 8x port you are ok, you can get like an IBM BR10 or something similar. Your files are on a RAID matrix or you simply have a lot of drives?
With 2 Opterons [email protected] I have been told that FAH numbers should be comparable to a Phenom II X6 @ 3.6 GHz so around 12-14k PPD